Methods and apparatus for perforating earth formations

ABSTRACT

This application discloses new and improved methods for perforating earth formations and then cleaning debris and the like from such perforations. To practice the present invention, a new and improved perforator is provided with one or more pairs of like or similar perforating devices operatively arranged for producing perforations in an earth formation which are selectively directed so that each pair of perforations will be in fluid communication with each other. An enclosed low-pressure chamber is coupled to one of the perforating devices in each set and a seal is arranged around the perforating axis of this perforating device for at least limiting the direct entrance of well bore fluids into the perforation produced thereby. In this manner, upon operation of each pair of the perforating devices, well bore fluids will be drawn into the perforation produced by the other perforating device and be swept through the intercommunicating perforations into the low-pressure chamber for cleaning debris and loose formation materials from the perforations.

United States Patent 3,347,315 /1967 Lanmon 166/100X [72] Inventor CPLanmon, II

Friendswwdflex- 3,395,758 8/1968 Kelly etal 166/100 [21] p 38953 PrimaryExaminerDavid H. Brown [22] Filed May 20, 1970 Attorneys-Ernest R.Archambeau, Jr., David L. Moseley, [45] Patented Dec. 28, 1971 Ed dM R RSh [73] Assignee Schlumberger Technology Corporation war oney an 1 mmeman New York, NY.

ABSTRACT: This application discloses new and improved [54] METHODS ANDAPPARATUS FOR PERFORATING methods for perforating earth formations andthen cleaning debris and the like from such perforations. To practicethe EARTH FORMATIONS d d rf d Claims 4 Drawing Figs. present invention,a new an improve pe orator is prov e with one or more pairs of like orsimilar perforating devices [52] U.S.Cl 166/297, operatively arrangedfor producing perforations in an earth 166/100 formation which areselectively directed so that each pair of Int. Cl 1.. ..E2lb 43/117rforations will be in fluid communication with each other. 5 Field of@Qfl'glh 1 /297, An enclosed low-pressure chamber is coupled to one ofthe 100, 55.1; 175/452, 4.6 perforating devices in each set and a sealis arranged around the perforating axis of this perforating device forat least limit- [56] References Cned ing the direct entrance of wellbore fluids into the perforation UNITED STATES PATENTS produced thereby.In this manner, upon operation of each pair 2,796,023 6/1957 Abendroth175/452 of the performing devices, bore fluids will be drawn into3,329,204 7/1967 Brieger 166/100 X the perforation produced by the otherperforating device and 3,346,057 10/1967 Bell 175/452 be swept throughthe intercommunicating perforations into 3,347,314 10/1967 Schuster166/100 x the low-pressure chamber forcleaning debrisand loose formationmaterials from the perforations.

Q as 65 v 21 PATENTED DEE28 I971 SHEET 1 BF 2 C P Lanmon,1I

N VE N TOR ATTORNEY METHODS AND APPARATUS FOR PERFORATING EARTHFORMATIONS It is, of course, customary for a cased well bore to beperforated at one or more points to provide fluid communication withselected earth formations therearound. Once the well is perforated,various treating operations-such as acidizing, fracturing, orsand-consolidating operations-are typically conducted to prepare thewell for efficient production. Those skilled in the art will appreciate,however, that it is not at all uncommon for one or more of theperforations along a given perforated interval to be at least partiallyblocked by loose formation materials, debris, as well as foreign matterwhich is usually deposited in a perforation by a typical shaped charge.A partial or total blockage of one or more of the perforations will, ofcourse, impede or prohibit the introduction of treating fluids intothose perforations and result in the inadequate treatment of at leastthose portions of the earth formation immediately adjacent thereto. As aresult, further and otherwise needless treating operations willultimately be required. Accordingly, unless all of the perforationsalong a perforated interval are capable of readily conducting fluids,subsequent treating operations as well as the production rate of thewell will be significantly impaired.

I-Ieretofore, substantial effort has been directed toward devisingperforating apparatus and techniques for cleaning perforations in thosesituations where the formation to be perforated is substantiallycomposed of loose or incompetent formation materials which must bechemically bonded to limit the subsequent production of these loosematerials. For example, in U.S. Pat. No. 3,153,449, unique methods andapparatus are disclosed for producing a single perforation that is firstflushed of loose formation materials and then injected with a suitabletreating agent for consolidating the immediately surrounding portion ofthe formation. Similarly, U.S. Pat. No. 3,329,204, US. Pat. No.3,347,314, and U.S. Pat. No. 3,347,315, respectively disclose new andimproved techniques and tools for perforating a well casing at twoclosely spaced points and, after clearing the perforations of looseformation materials, injecting suitable consolidation agents.

Although the several tools and techniques described in theaforementioned patents have been commercially employed, it will beappreciated that only one or, at best, two usable perforations areproduced for each operation. Thus, if a formation interval ofsubstantial length is' to be perforated at several spaced points, toolssuch as these must be repetitively employed before the entire intervalcan be sufficiently perforated.

It will be appreciated, moreover, that none of these techniques orperforating tools are particularly suited for those situations where theformation that is to be perforated is competent and does not require theinjection of a consolidating agent. Furthermore, with the possibleexception of the techniques and tools disclosed in U.S. Pat. No.3,305,018, little attention has been given heretofore for devisingsuitable procedures and perforating apparatus which are effective forperforating well-consolidated formations at a number of spaced locationsand then cleaning the perforations in a single trip into a well bore.

Accordingly, it is an object of the present invention to provide new andimproved methods for producing multiple debris-free perforations atspaced locations along a well bore interval traversing an earthformation irrespective of the competency of the formation.

This and other objects of the present invention are attained byarranging multiple sets of similar or like perforating devices at spacedintervals along a supporting carrier, with the perforating devices ineach set being cooperatively directed so that their perforating axeswill converge or at least approach an intersection within an earthformation ahead of the carrier. Means are further provided for enclosingone of the perforating devices in each set and fluidly coupling theenclosure surrounding the selected device to an enclosed chamber whichis initially unfilled and is maintained at a pressure less than that ofthe fluids in the well bore adjacent to a formation that is to beperforated in accordance with the methods of the present invention.Means are operatively arranged on the carrier and adapted, upon movementof the carrier to a selected position in a well bore, for at leastsubstantially blocking the direct entrance of well bore fluids into theenclosures associated therewith whenever the selected perforatingdevices are operated. In this manner when the new and improvedperforating apparatus is employed for practicing the methods of thepresent invention, operation of the perforating devices in each set willproduce perforations in the formation which will be effectual forestablishing fluid communication so that well bore fluids will sweepthrough the circuitous passage defined in the formation by thecooperatively directed perforations for flushing debris and the liketherefrom and into the enclosed chamber.

The novel features of the present invention are set forth withparticularity in the appended claims. The invention, together withfurther objects and advantages thereof, may be best understood by way ofthe following description of exemplary methods employing the principlesof the invention as illustrated in the accompanying drawings, in which:

FIG. 1 depicts a preferred embodiment of perforating apparatusincorporating the principles of the present invention as this apparatuswill appear positioned in a well bore while conducting a perforatingoperation in accordance with the methods of the present invention;

FIG. 2 is an enlarged cross-sectioned elevational view of a portion ofthe perforating apparatus depicted in FIG. 1;

FIG. 3 is a cross-sectional view taken along the lines "3-3" of FIG. 2;

FIG. 4 is an enlarged view of another portion of the perforatingapparatus shown in FIG. 1;

FIG. 5 is a cross-sectional view taken along the lines 5-5 of FIG. 4;and

FIGS. 6 and 7 respectively depict the production of one pair ofperforations in accordance with the methods of the present invention.

Turning now to FIG. I, perforating apparatus 10 arranged in accordancewith the present invention is shown suspended in a typical manner froman electrical cable 1 1 within a casing 12 that is secured within aborehole 13 by a column of cement 14. The suspension cable 11 is spooledfrom a winch (not shown) at the earth's surface that is adapted forselectively moving the perforating apparatus 10 through the casing 12 tobring the perforator into position adjacent to an earth formation 15which is to be perforated in accordance with the methods of the presentinvention.

The perforating apparatus 10 for practicing the present inventionincludes an elongated body or carrier I6 which is conveniently arrangedas a series of housing sections, as at 17-19, which are coupled to aplurality of tandemly arranged perforating units as at 20 and 21 forperforming a given perforating operation. As is typical, suitabledepth-indicating means, such as a casing-collar locator, are arranged inone of the sections as at 17; and, in the preferred embodiment of theapparatus 10, another section 18 of the carrier 16 is appropriatelyarranged for enclosing an electrical control system such as that shownin U.S. Pat. No. 3,327,791, for selective operation of the perforatingapparatus. For reasons that will subsequently be explained in greaterdetail, positioning means, such as rearwardly acting opposed springs22-25 of a new and improved design, are mounted adjacent to the upperand lower ends of the carrier 16 and cooperatively arranged for urgingthe carrier forwardly to maintain the forward faces of a plurality ofsealing means, as at 26, respectively mounted on each of the perforatingunits 20 and 21 in continuous sliding engagement with the adjacent wallof the casing 12.

Turning now to FIG. 2, an enlarged view is shown of the upperperforating unit 20 which is similar or identical to the other units, asat 21, coupled therebelow. In the illustrated preferred embodiment, acylindrical body 27 is arranged to include two longitudinally spacedlateral chambers 28 and 29 which are respectively proportioned toenclose perforating means, such as a shaped charge as at 30 and 31. Inkeeping with the objects of the present invention, the shaped chargechambers 28 and 29 are respectively formed about laterally directed axes32 and 33, with the axis of the upper chamber being tilted downwardly toconverge and, preferably, intersect the axis of the lower chamber at aselected distance ahead of the forward face (to the right as viewed inFIG. 2) of the body 27. A third chamber 34 of a predetermined volume isformed in the lower portion of the body 27 and fluidly coupled to theintermediate chamber 29 as by an interconnecting passage 35 in the body.

Although-other coupling arrangements can, of course, be provided for theseveral perforating units 20 and 21, it is preferred to arrange eachunit with a reduced-diameter upper end, as at 36, that is sealinglyfitted, as by an O-ring 37, into the chamber 34 in the unit thereaboveto close the lower end of the chamber. By means of suitable screws, asat 38, the perforating units 20 and 21 can be secured together andproperly oriented to accurately direct their respective shaped charges30 and 31 forwardly of the carrier 16. In the preferred embodiment ofthe tool 10, a removable plug, as at 39, is provided for draining thechamber 34 through a suitable port 40. It will, of course, be recognizedthat the lowermost section 19 of the carrier 16 is appropriatelyarranged to close the lower chamber (as at 34 in the unit 20) in thelowermost perforating unit. Similarly, the housing section 18 isappropriately arranged to sealingly receive the upper end portion of theupper perforating unit 20.

To gain access to the upper chamber 28, an enlarged lateral port 41 ofsufficient size to permit the introduction of the shaped charge 30 intothe chamber is arranged in a downwardly and inwardly inclined flatsurface 42 formed transversely across the forward wall of the body 27and, preferably, perpendicularly intersecting the inclined lateral axis32. A port-closure plug 43 is secured in the port 41, as by threads 44,and cooperates with a sealing member 45 for fluidly sealing the shapedcharge 30 within the upper chamber 28. In a similar fashion, a flattransverse surface 46 is formed across the forward wall of the body 27;and a lateral port 47 therein is coaxially arranged about the axis 33and suitably sized for admitting the shaped charge 31 into theintermediate chamber 29.

Although the shaped charges 30 and 31 may, of course, be of otherdesigns, it is preferred that they be similar or identical to thosedisclosed in US. Pat. No. 3,329,218. Accordingly, as fully explained inthat patent, lateral bores 48 and 49 are respectively provided in therear wall of the body 27 in coincidental alignment with the perforatingaxes 32 and 33 and appropriately arranged for respectively receivingelectrical contactors 50 and 51 (such as those shown at 28 in theaforementioned patent) and detonating means such as electricallyactuated initiators 52 and 53 (such as those shown at 44" in theaforementioned patent) to enable the shaped charges 30 and 31 to beselectively detonated from the surface by operation of the controlsystem in the carrier section 18. Inasmuch as the particular details ofthe shaped charges 30 and 31 an their respective detonators orinitiators 52 and 53 are of no significance to the present invention,further description is unnecessary.

Turning now to the new and improved sealing means 26 as best illustratedin F 108. 2 and 3, the access port 47 is preferably threaded, as at 54,for cooperatively receiving the rearward portion of a closure member 55having an elongated forward tubular portion 56 and an intermediateshoulder or outwardly enlarged flange 57 adapted for engagement againstthe flat surface 46. A sealing member 58 is cooperatively arranged tofluidly seal the closure member 55 in relation to the body 27. Toprevent the entrance of well fluids into the intermediate chamber 29until the shaped charge 31 therein is detonated, a transverse web, as at59, is arranged across the forward tubular portion 56 and, preferably,positioned at the extreme forward end thereof. Although it couldalternatively be made integral with the closure member 55, a separatetubular member 60 is coaxially fitted over the forward portion 56 of theclosure member and, for reasons that will subsequently be explained,extended forwardly thereof a sufficient distance to at least projectbeyond the curvature of the forward wall of the body 27.

In the preferred embodiment of the sealing means 26, an annular sealingpad 61 of a sturdy elastomeric material is coaxially fitted over thetubular extension 60 and secured to the flat body surface 46. Althoughthe initial configuration of the forward face of the sealing pad 61 isnot critical in accomplishing the objects of the present invention, itis preferred to initially shape the forward face of the sealing member(as best seen in F IG. 3) to substantially conform to the curvature ofthe internal wall of the casing 12. Where this is done, the tubularextension 60 is preferably arranged with a hexagonal exterior surfaceadapted for complementally fitting within the axial bore through thesealing pad 61 so as to prevent it from turning thereon out of itsinitial angular position. To prevent the sealing member 61 from beingdislodged form the body 27 as the perforating apparatus 10 is beingmoved into position in the well bore 13, the sealing member is providedwith an outwardly enlarged portion 62 which is overlayed by an annularretainer 63 and secured to the body 27 as by one or more screws (notshown). It will be appreciated, therefore, that once the shaped charge31 is enclosed within the intermediate chamber 29 and the closure member55, the sealing member 61 and the tubular extension 60 are respectivelysecured to the body 27, only the forwardmost portions of these lattertwo members will contact the inner wall of the casing 12 whenever theperforating apparatus 10 is urged theretoward by the upper and lowerpositioning springs 22-25.

It should be noted that longitudinally disposed bow springs could besubstituted for the new and improved positioning springs 22-25 withoutunduly affecting the unique operation of the remainder of theperforating apparatus 10. Those skilled in the art will recognize,however, that it will often be necessaryto introduce the perforatingapparatus 10 into a well bore by way of pressure-control equipment atthe surface such as blowout preventors, so-called lubricators, andsimilar restrictions. Thus, typical bow springs which can be readilycollapsed to pass such restrictions and still be capable of developingspring forces of the same magnitude as the new and improved positioningsprings 22 would be objectionably long. Accordingly, in the preferredembodiment of the new and improved positioning springs 22-25, eachspring is respectively comprised of a generally flat sheet of a somewhatresilient material such as spring steel or the like which will readilyflex. As best seen in FIG. 1, the forward edge of each of the severalsprings 22-25 is secured longitudinally along one or the other sides ofthe carrier 16, as by screws 64 and 65, so that the unrestrained orcantilevered portion of each spring will initially extend well behindthe rear wall of the carrier. It will be noted, therefore, that bylongitudinally offsetting the upper springs 22 and 23 and mounting thesprings on alternate sides of the carrier 16 as illustrated in FIG. 1and 3, each of these springs can be transversely flexed so as to curveit back around the rear of the carrier. The lower springs 24 and 25 aresimilarly arranged for functioning in the same manner. The transversedeflections of the positioning springs 22-25 will, of course, imposeforwardly acting spring forces on the carrier 16 which are commensuratewith the material employed, the extent of their deflection, as well astheir physical dimensions.

Accordingly, when the perforating apparatus 10 is first being loweredinto the well bore 13, the upper and lower springs 22-25 are manuallyflexed inwardly and back around the rear of the carrier 16 as requiredfor introducing the perforating apparatus into the casing 12 at thesurface of the earth. Then, as best seen in FIG. 3, once the perforatingapparatus 10 is disposed within the casing 12, each of the springs 22-25will assume a generally arcuate curvature around the rear of the carrier16 so that their longitudinal rearward edges,

as at 66 and 67, will respectively contact the wall of the casing behindthe carrier and somewhat on the opposite side thereof from where thatparticular spring is secured. Thus, by virtue of the alternatedisposition of the springs 22-25 along the rear of the carrier 16, thecarrier will be reliably positioned within the casing 12 so that as thetool is lowered into the well bore 13 the forwardmost portions of theextension members 60 and the sealing pads 61 will always be urgedsquarely against the adjacent wall of the casing.

According, in view of the continued abrasion of the casing 12 againstthe sealing member 61 and the tubular extension 60 of each of theperforating units 20 and 21 as the perforating apparatus 10 is movedinto position adjacent to the earth formation15, the sealing members andtheir associated tubular extensions will be progressively ground orlapped to complementally fit the curvature of the casing. In thismanner, it will be assured that by the time the perforating apparatus 10is positioned adjacent to the earth formation 15, at least the forwardend of the tubular extension 60 and the forward face of the elastomericsealing member 61 will closely conform to the internal configuration ofthe casing 12.

It will be appreciated, however, that the amount of material that willbe progressively abraded form the tubular extension 60 and the sealingmember 61 of each of the several perforating units as at 20 and 21 will,for the large part, be directly related to the distance which theperforating apparatus 10 moves through the well bore 13. For example, ina relatively shallow well, the amount of wear experienced by the tubularextensions 60 and the sealing members 61 will be correspondingly slight.On the other hand, should the earth formation 15 be at a substantialdepth in the well bore 13, the tubular extensions 60 as well as theforward faces of the sealing members 61 might well be unduly worn by thetime that the perforating apparatus 10 has finally reached its finalposition.

Accordingly, as best seen in FIGS. 4 and 5, to limit the amount of wearor abrasion to which the several sealing members 61 and the tubularextensions 60 will be subjected, upper and lower pairs of forwardlyprojecting lugs, as at 68 and 69, are respectively arranged near theupper and lower ends of the carrier 16 to prevent these several membersfrom being excessively abraded by the time the perforating apparatus 10is adjacent to the formation 15. It will be recognized, of course, thatthe wear-limiting lugs 68 and 69 will be arranged to allow the sealingmembers 61 and the tubular extensions 60 to always be sufficientlyabraded to closely fit the curvature of the internal wall of the casing12. In the preferred manner of accomplishing this, each of the severalwear-limiting lugs 68 and 69 is comprised of a small block 70 of ahardened or abrasionresistant material such as tungsten carbide or thelike that is secured as by screws 71 to the carrier 16. The forwardupright edges of each of the several hardened blocks, as at 70, arecooperatively positioned at a predetermined distance away from theforward face of the carrier 16 so that, once the sealing members 61 andthe tubular extensions 60 have been sufficiently ground down to assurethat their forward surfaces complementally fit the curvature of thecasing 12, the several blocks will substantially limit, if notaltogether prevent, further abrasion of the sealing members and theextensions. To protect the blocks 70 from striking inward projections inthe casing 12 as the tool 10 is being moved therein, shoulders as at 72are preferably provided above and below the blocks.

It will be appreciated that the perforating apparatus 10 can be normallyexpected to be employed in various sizes of casing. Accordingly, topermit a ready adjustment of the guides 68 and 69, each of the severalblocks 70 is adapted to be selectively secured in one of at least twopredetermined positions in relation to the carrier 16. To facilitate theplacement of the blocks 70 in these predetermined positions, selectivelyarranged seating surfaces, as at 73 and 74, are formed at appropriatepositions on the carrier 16 so that each of the hardened blocks can bereadily secured to accurately position their outer edges at the correctposition for sliding engagement with the inner wall of a given casingsize once the sealing pads 61 and the tubular extensions 60 are lappedinto conformity with the casing wall.

Referring again to FIG. 1, it will be appreciated that once theperforating apparatus 10 is moved into position adjacent to theformation 15, the perforating units as at 20 and 21 are in readiness forperforating the casing 12 and the cement 14 to gain access to the earthformation Thus, as best seen in FIG. 6 upon detonation of the shapedcharge 30 in, for example, the upper perforating unit 20, a perforation75 will be produced along the axis 32 into the adjacent earth formation15. The detonation of the upper shaped charge 30 will produce aperforating jet which, as is well known in the art, will leave debrissuch as a slug 76 in the forward portion of the perforation 75 as wellas a relatively impermeable sheath or layer of debris as at 77 along thewalls of at least a substantial portion thereof.

Accordingly, in keeping with the objects of the present invention,detonation of the second shaped charge 31 in the perforating unit 20will, as depicted in FIG. 7, produce a perforation as at 78 whichsubstantially intersects the first perforation 75 so as to form acircuitous passage in the formation 15 through which the fluids in thewell bore 13 can enter the enclosed low-pressure chamber 34 in theperforating unit. Thus, as schematically indicated by the arrow 79, oncethe perforating jet produced by the second shaped charge 31 pierces thetransverse barrier 59 and produces the second perforation, the well borefluids will rush through the intersecting perforations 75 and 78 intothe low-pressure chamber 34. it will be appreciated, therefore, that therapid flow of these fluids 79 will flush the debris (as at 76 and 77)from the perforation 75 as well as similar debris (not shown) in thesecond perforation 78. Moreover, it is believed that the sudden inrushof the well bore fluids will also be effective for removing any looseformation materials in both of the perforations 75 and 78 so that, oncethey are enlarged as depicted, the flow capabilities of the perforationswill be significantly improved over what would otherwise be expected forperforations produced by prior perforating techniques.

It should be noted that the competency of the formation 15 will, ofcourse, largely determine the degree of enlargement of the perforations75 and 78 that will result from the rapid influx of the well bore fluidstherethrough. Thus, should the formation 15 be relativelyunconsolidated, it is expected that a substantial cavity will be formed(such as depicted at 88" in U.S. PAT. No. 3,347,314). In any event,therefore, a significant improvement in the flow characteristics of theperforations 75 and 78 will be achieved by the practice of the presentinvention.

Those skilled in the art will, of course, appreciate that theperforations 75 and 78 should be protected against the usual wellcontrol fluid or so-called mud" typically used during the drilling of awell. Thus, if the present invention is to be practiced prior to afracturing or acidizing operation, any one of several techniques may beemployed to protect the perforations from damage by unclean well controlfluids. For example, the drilling mud may be replaced with a cleansaline solution of sufficient density to retain control of the well.Similarly, the well control fluid may also be replaced with a cleandiesel oil or other fluids that are compatible with or may be employedin a subsequent fracturing or acidizing operation. It will, of course,be recognized that the well control fluid might be a pressured gas. Inthose situations, the pressured gas would be expected to effectivelyflush the perforations 75 and 78.

The same situation will, of course, exist where the formation 15 isrelatively incompetent and the methods of the present invention areemployed in preparation for an otherwise typical sand-consolidationoperation. Thus, where sand-consolidation agents are to be subsequentlyinjected into the formation 15, the well control fluid may be replacedby the initial treating agent which is usually a so-called preflushfluid" such as kerosene, diesel oil, or a clean saline solution.

Other techniques may also be employed for protecting the perforations 75and 78 produced by the present invention For example, before theperforating apparatus 10 is positioned in the well bore 13, the wellcontrol fluids at least immediately adjacent to the formation may bereplaced with a suitable temporary plugging agent such as gelledkerosene, gelled carbon tetrachloride, or such commercially availableprotective formulations as Black magic" as sold by Oil Base, lnc., PerfHeal" as sold by Chemical Additives Company, or Plug Ban" as soldbyl-lumble Oil & Refining Company, all of which are located in Houston,Texas. Any suitable fluid or other agent can, of course, be used so longas it does not react adversely with either the formation materials orconnate fluids and can be readily removed form a perforation when thewell is produced.

It should be noted that the sequence of firing the several perforatingunits as at and 21 as well as their respective shaped charges and 31 isflexible. The control system in the housing section 18 can, of course,be adapted to actuate the perforating units as at 20 and 21 in anydesired order either in groups or individually. Similarly, the shapedcharges 30 and 31 in any of the several perforating units as at 20 and21 can be selectively detonated either in any order or simultaneously.Thus, it will be appreciated that the perforating apparatus 10 of thepresent invention is readily suited for any perforating operation.

As previously described, the cooperative relationship of thewear-limiting lugs 68 and 69 and the several sealing means 26 willassure that the forward end of each of the tubular extensions 60 will belapped or ground down so as to closely conform to the curvature of thecasing 12 once the perforating apparatus 10 is adjacent to the formation15. Thus, it is believed that the sealing pads 61 may not necessarily beessential to the successful practice of the present invention since, atbest, there could only be an insignificant flow of well bore fluidsthrough whatever minute gap might be present between the casing wall andthe well-lapped forward end of the tubular extensions 60. It is,however, preferred to include the sealing pads 61 with the sealing means26 as a preventative measure since the forward ends of one or more ofthe tubular extensions 60 might be damaged as the perforating apparatus10 is moved through the casing 12.

Those skilled in the art will, of course, appreciate that since theupper perforations, as at 75, are in communication with the well borefluids, the pressure in the chambers 34 will rapidly become equal to thewell bore hydrostatic pressure once the chambers are filled.Accordingly, it is of significance to note that, in contrast to thepreviously described prior perforating techniques, the perforatingapparatus 10 cannot become differentially stuck as would be the case ifpressure communication is not established between the well bore fluidsand the several chambers 34 once the perforations 75 and 78 have beenproduced.

Accordingly, it will be appreciated that the present invention hasprovided new and improved methods for producing multiple perforations inearth formations of various degrees of competency and then cleaningthese perforations to assure improved flow communication between thewell bore and the perforated formations. Once the new and improvedperforating apparatus disclosed herein is positioned, detonation of theseveral pairs of shaped charges will produce a corresponding number ofintercommunicating flow passages in the formation between the well borefluids and the initially enclosed chambers for inducing a rapid influxof these fluids through the flow passages to clear them of debris andother flow-blocking materials.

While a particular embodiment of the present invention has been shownand described, it is apparent that changes and modifications may be madewithout departing from this invention in its broader aspects; and,therefore, the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope of thisinvention.

What is claimed is:

1. A method for completing a well bore containing fluids and traversingearth formations and comprising the steps of:

isolating a plurality of spaced surfaces along the well bore from thewell bore fluids; perforating said spaced surfaces to provide a numberof passages into the earth formations which are isolated form the wellbore fluids; perforating a plurality of exposed surfaces along the wellbore and adjacent to said spaced surfaces to provide a number .of openpassages into the earth formations which are respectively directed inrelation to said isolated passages to be effectual for communicatingtherewith; and, while said spaced surfaces are still isolated, couplinga receiver at a pressure less than that of the well bore fluids intosaid isolated passages for drawing well bore fluids into said openpassages and back out of said isolated passages into said receiver toclean said passages.

2. The method of claim 1 wherein said spaced surfaces are distributedlongitudinally along the well bore.

3. The method of claim 1 wherein said spaced surfaces are distributedlongitudinally along the well bore and the exposed surfaces arealternately distributed along the well bore between said spacedsurfaces.

4. The method of claim 1 wherein the number of said isolated passages isequal to the number of said open passages so that only one of each ofsaid open passages will establish communication with only one of saidisolated passages adjacent thereto.

5. The method of claim 4 wherein said spaced surfaces are distributed atlongitudinal intervals along the well bore and the exposed surfaces arealternately distributed therebetween.

6. The method of claim 5 wherein said spaced surfaces and said exposedsurfaces are longitudinally aligned with one another.

7. The method of claim 1 wherein each of one set of said passages isdirected along an axis substantially normal to the wall of the well boreand each of the other set of said passages is directed along an axissubstantially intersecting the axis of the adjacent passage of said oneset.

8. The method of claim 1 wherein a separate receiver is coupled to eachof said isolated passages 9. The method of claim 1 wherein the well borefluids include liquids having an elevated hydrostatic pressure.

10. The method of claim 1 wherein the well bore fluids include gases atan elevated pressure.

11. The method of claim 1 wherein said open passages and said isolatedpassages are simultaneously produced.

12. The method of claim 1 wherein said open passages are produced beforesaid isolated passages 13. The method of claim 1 wherein said isolatedpassages are produced before said open passages.

14. The method of claim 1 wherein said passages are produced in analternating sequence.

15. A method for completing a well bore containing fluids and traversingan earth formation and comprising the steps of: isolating a firstsurface of the well bore from the well bore fluids and from a secondadjacent surface of the well bore; perforating through one of saidsurfaces and into the formation to provide a first passage therein;perforating through the other of said surfaces and into the formation toprovide a second passage therein directed relative to said first passageto be effectual for establishing fluid communication therebetween; and,thereafter, coupling a receiver at a pressure less than that of the wellbore fluids to said isolated surface and the passage therein for drawingwell bore fluids into the other passage and out through the passage insaid isolated surface into said receiver to flush unwanted material outof said passages and into said receiver.

16. The method of claim 15 wherein said first and second passages arerespectively directed along converging axes.

17. The method of claim 15 wherein one of said passages is directedalong a first axis substantially normal to the wall of the well bore andthe other of said passages is directed along a second axis whichsubstantially approaches an intersection with said first axis.

18. The method of claim 15 wherein said passages are sequentiallyproduced.

19. The method of claim wherein said passages are produced substantiallysimultaneously.

20. The method of claim 15 wherein said first surface is longitudinallyspaced from said second surface and is vertically aligned therewith.

21. The method of claim 15 wherein the well bore fluids include liquidshaving an elevated hydrostatic pressure.

22. The method of claim 15 wherein the well bore fluids include gases atan elevated pressure.

23. The method of claim 15 wherein said passages are respectivelyproduced by shaped charge perforating devices so that said unwantedmaterial may include debris deposited in said passages by said shapedcharge perforating devices.

24. A method for perforating a cased well bore containing fluids andtraversing earth formations and comprising: enclosing a firstperforating device within a hollow carrier having an outstanding memberon one side thereof and in alignment with said first perforating device;mounting a second perforating device on said carrier and directing saidsecond perforating device along an axis substantially intersecting theaxis of said first perforating device; placing said carrier into a casedwell bore and urging said carrier laterally to position said outstandingmember against the adjacent wall of the well casing; lowering saidcarrier into the well bore while said outstanding member is maintainedagainst the adjacent casing wall to abrade said outstanding member intoa curvature substantially complementary with the curvature of the casingwall; and actuating said perforating devices to produce first and secondsubstantially intersecting passages in the earth formations with saidfirst passage being substantially isolated from the well bore fluids bythe complemental fit of said outstanding member with the casing wall andsaid second passage being in communication with the well bore fluids forinducing a flow of such fluids through said passages and into saidcarrier to clean said passages.

25. The method of claim 28 wherein said perforating devices are shapedcharges.

k 1F i

1. A method for completing a well bore containing fluids and traversing earth formations and comprising the steps of: isolating a plurality of spaced surfaces along the well bore from the well bore fluids; perforating said spaced surfaces to provIde a number of passages into the earth formations which are isolated form the well bore fluids; perforating a plurality of exposed surfaces along the well bore and adjacent to said spaced surfaces to provide a number of open passages into the earth formations which are respectively directed in relation to said isolated passages to be effectual for communicating therewith; and, while said spaced surfaces are still isolated, coupling a receiver at a pressure less than that of the well bore fluids into said isolated passages for drawing well bore fluids into said open passages and back out of said isolated passages into said receiver to clean said passages.
 2. The method of claim 1 wherein said spaced surfaces are distributed longitudinally along the well bore.
 3. The method of claim 1 wherein said spaced surfaces are distributed longitudinally along the well bore and the exposed surfaces are alternately distributed along the well bore between said spaced surfaces.
 4. The method of claim 1 wherein the number of said isolated passages is equal to the number of said open passages so that only one of each of said open passages will establish communication with only one of said isolated passages adjacent thereto.
 5. The method of claim 4 wherein said spaced surfaces are distributed at longitudinal intervals along the well bore and the exposed surfaces are alternately distributed therebetween.
 6. The method of claim 5 wherein said spaced surfaces and said exposed surfaces are longitudinally aligned with one another.
 7. The method of claim 1 wherein each of one set of said passages is directed along an axis substantially normal to the wall of the well bore and each of the other set of said passages is directed along an axis substantially intersecting the axis of the adjacent passage of said one set.
 8. The method of claim 1 wherein a separate receiver is coupled to each of said isolated passages
 9. The method of claim 1 wherein the well bore fluids include liquids having an elevated hydrostatic pressure.
 10. The method of claim 1 wherein the well bore fluids include gases at an elevated pressure.
 11. The method of claim 1 wherein said open passages and said isolated passages are simultaneously produced.
 12. The method of claim 1 wherein said open passages are produced before said isolated passages
 13. The method of claim 1 wherein said isolated passages are produced before said open passages.
 14. The method of claim 1 wherein said passages are produced in an alternating sequence.
 15. A method for completing a well bore containing fluids and traversing an earth formation and comprising the steps of: isolating a first surface of the well bore from the well bore fluids and from a second adjacent surface of the well bore; perforating through one of said surfaces and into the formation to provide a first passage therein; perforating through the other of said surfaces and into the formation to provide a second passage therein directed relative to said first passage to be effectual for establishing fluid communication therebetween; and, thereafter, coupling a receiver at a pressure less than that of the well bore fluids to said isolated surface and the passage therein for drawing well bore fluids into the other passage and out through the passage in said isolated surface into said receiver to flush unwanted material out of said passages and into said receiver.
 16. The method of claim 15 wherein said first and second passages are respectively directed along converging axes.
 17. The method of claim 15 wherein one of said passages is directed along a first axis substantially normal to the wall of the well bore and the other of said passages is directed along a second axis which substantially approaches an intersection with said first axis.
 18. The method of claim 15 wherein said passages are sequentially produced.
 19. The method of claim 15 wherein said passages are produced substantially simultaneously.
 20. The method of claim 15 wherein said first surface is longitudinally spaced from said second surface and is vertically aligned therewith.
 21. The method of claim 15 wherein the well bore fluids include liquids having an elevated hydrostatic pressure.
 22. The method of claim 15 wherein the well bore fluids include gases at an elevated pressure.
 23. The method of claim 15 wherein said passages are respectively produced by shaped charge perforating devices so that said unwanted material may include debris deposited in said passages by said shaped charge perforating devices.
 24. A method for perforating a cased well bore containing fluids and traversing earth formations and comprising: enclosing a first perforating device within a hollow carrier having an outstanding member on one side thereof and in alignment with said first perforating device; mounting a second perforating device on said carrier and directing said second perforating device along an axis substantially intersecting the axis of said first perforating device; placing said carrier into a cased well bore and urging said carrier laterally to position said outstanding member against the adjacent wall of the well casing; lowering said carrier into the well bore while said outstanding member is maintained against the adjacent casing wall to abrade said outstanding member into a curvature substantially complementary with the curvature of the casing wall; and actuating said perforating devices to produce first and second substantially intersecting passages in the earth formations with said first passage being substantially isolated from the well bore fluids by the complemental fit of said outstanding member with the casing wall and said second passage being in communication with the well bore fluids for inducing a flow of such fluids through said passages and into said carrier to clean said passages.
 25. The method of claim 28 wherein said perforating devices are shaped charges. 